Braking and driving device for the shuttle of a weaving loom

ABSTRACT

The device includes a plurality of driven pulleys arranged consecutively in the shuttle shot direction with at least those pulleys serving to brake the shuttle being selectively movable into a working position, in which they cooperate with the shuttle moving in the shuttle guide box, and into an inoperative position and being driven at respective peripheral speeds which decrease in the direction of shuttle movement. The pulleys serving to brake the shuttle are mounted for conjoint displacement in a plane transverse to the pulley axes and are biased toward the shuttle race. The respective distances between the pulley peripheries and the shuttle race decrease in the direction of shuttle movement with the greatest of such distances, when the pulley peripheries are not engaged with the shuttle, being not in excess of the thickness of the shuttle. The pulleys serving to brake the shuttle may be mounted on an elongated bar which is bodily movable in a plane perpendicular to the pulley axes, or the bar may be tiltable in a plane perpendicular to the pulley axis. In a preferred embodiment, the pulleys serving to brake the shuttle are rotatably mounted on respective cranks hinged at fixed pivots and having their free ends interconnected by a bar for conjoint movement of the cranks. The braking pulleys acting last upon the shuttle, in the direction of shuttle movement, have a frictional connection to their respective drives for rotation relative to the respective drives, the friction moment between each of these pulleys and its drive being less than the frictional force acting upon the pulley peripheries in engagement with the shuttle.

United States Patent 1 Porter 1 June 17, 1975 1 BRAKING AND DRIVING DEVICE FOR THE SHUTTLE OF A WEAVING LOOM {75] Inventor: Allan William Henry Porter,

Lustmuhle, Ar, Switzerland [73] Assignee: Aktiengesellschaft Adolph Saurer,

Switzerland 22 Filed: Dec. 13, 1973 211 Appl. No.: 424,543

Related US. Application Data [63] Continuation-impart of Ser. No. 375,867, July 2,

1973, abandoned.

[30] Foreign Application Priority Data Sept. 4, 1972 Switzerland 12991/72 Aug. 22, 1973 Switzerland [1426/73 [52] U.S. Cl 139/142; 139/186 [51] Int. Cl. D03d 49/24; D03d 49/54 [58] Field of Search 139/142, 147, 133, 185, 139/186, 187

[56] References Cited UNITED STATES PATENTS 59,767 11/1866 Harrison et a1. 139/142 2,082,896 6/1937 Lindegren et al..., 3,587,667 6/1971 Porter 139/142 FOREIGN PATENTS OR APPLICATIONS 448,393 5/1949 ltaly 139/133 350,417 3/1922 Germany 139/142 Primary Examiner,lames Kee Chi Attorney, Agent, or FirmMcGlew and Tuttle [57] ABSTRACT The device includes a plurality of driven pulleys arranged consecutively in the shuttle shot direction with at least those pulleys serving to brake the shuttle being selectively movable into a working position, in which they cooperate with the shuttle moving in the shuttle guide box, and into an inoperative position and being driven at respective peripheral speeds which decrease in the direction of shuttle movement. The pulleys serving to brake the shuttle are mounted for conjoint displacement in a plane transverse to the pulley axes and are biased toward the shuttle race. The respective distances between the pulley peripheries and the shuttle race decrease in the direction of shuttle movement with the greatest of such distances, when the pulley peripheries are not engaged with the shuttle, being not in excess of the thickness of the shuttle. The pulleys serving to brake the shuttle may be mounted on an elongated bar which is bodily movable in a plane perpendicular to the pulley axes, or the bar may be tiltable in a plane perpendicular to the pulley axis. In a preferred embodiment, the pulleys serving to brake the shuttle are rotatably mounted on respective cranks hinged at fixed pivots and having their free ends interconnected by a bar for conjoint movement of the cranks. The braking pulleys acting last upon the shuttle, in the direction of shuttle movement, have a frictional connection to their respective drives for rotation relative to the respective drives, the friction moment between each of these pulleys and its drive being less than the frictional force acting upon the pulley peripheries in engagement with the shuttle.

10 Claims, 6 Drawing Figures PATENTEDJUN 17 1975 SHEET BRAKING AND DRIVING DEVICE FOR THE SHUTTLE OF A WEAVING LOOM CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 375,867, filed July 2, I973, for Braking and Driving Device for the Shuttle of a Weaving Loom", now abandoned.

FIELD AND BACKGROUND OF THE INVENTION The invention relates to a braking and driving device for the shuttle of a weaving loom, of the type including a plurality of driven pulleys, or pairs of pulleys looped by an endless belt, which are arranged consecutively in the shuttle shot direction with at least those pulleys serving to brake the shuttle being selectively movable into a working position, in which they cooperate with the shuttles, or into an inoperative position, and being driven at respective circumferential or peripheral speeds which decrease in the direction of shuttle movement.

In a known device of this type, the pulleys provided for braking and accelerating are arranged adjacent each other and can be brought from their working position into their inoperative position, or conversely, automatically by means of a change-over mechanism. Such a device is shown in Swiss Pat. No. 491,226. In the known device, owing to the change-over mechanism, the pulley, or the pair of pulleys, which has just been passed by the shuttle head is lifted at the moment when the shuttle comes into contact with the following slower turning pulley or pair of pulleys, as seen in the shot direction, so that the faster turning pulley or pair of pulleys no longer cooperates with the shuttle.

This known device requires a very precise running of the weaving loom so as to achieve the synchronism between the operation changing the pulleys from working into the inoperative position and the position of the shuttle. In addition, such a change-over controlling device is expensive.

SUMMARY OF THE INVENTION The present invention is directed to the problem of providing, for a braking and driving device of the type mentioned above, a more simple design in which at least those pulleys adapted to brake the shuttles can be shifted from their working position into their inoperative position by the shuttle itself.

In accordance with the invention, there is provided a device in which the pulleys, or at least those functioning to brake the shuttle, are conjointly displaceable in a plane transverse to the pulley axes and are urged toward the shuttle guide box. The respective distances between the circumferences or peripheries of the pulleys and the shuttle guide box decrease in the direction of shuttle movement during braking by the pulleys, that is, in the direction away from the selvage. In the rest position of the pulleys, and as long as no shuttle is in the shuttle box, the largest of these distances is equal, at the most, to the shuttle thickness.

With this arrangement, at the moment of the shuttle impinging on a pulley, the shuttle pushes the same away from the shuttle race and thereby, because it is provided that the pulleys can be displaced only jointly, the pulley which has already been passed and which rotates faster is lifted, so that only the following, slower rotating pulleys, further cooperate with the shuttle. Thus,

with the pulleys being controlled by the shuttle itself, the problem of synchronizing the positions of the pulley with the position of the shuttle can no longer arise.

An object of the invention is to provide an improved braking and driving device for the shuttle of a weaving loom.

Another object of the invention is to provide such a braking and driving device which has a more simple design and in which at least those pulleys which brake the shuttle can be shifted from their working position into their inoperative position by the shuttle itself.

A further object of the invention is to provide such a braking and driving device for the shuttle of a weaving loom in which at least those pulleys serving to brake the shuttle are conjointly displaceable in a plane transverse to the pulley axes and are biased toward the shut tle guide box.

For an understanding of the principles of the invention, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the Drawings:

FIGS. 1 and 2 are schematic elevation views illustrating the principle of two different arrangements of brak ing pulleys in accordance with the invention, the pul leys being represented in the plane of the shuttle guide box of a weaving loom;

FIG. 3 is a schematic elevational view showing analo gously and in the same plane, a constructional arrangement of a device embodying the invention;

FIG. 4 is a horizontal sectional view, taken on the line 4-4 of FIG. 5, illustrating the arrangement of FIG. 3 as embodied in practice;

FIG. 5 is a sectional view taken on the line 5-5 of FIG. 4; and

FIG. 6 is a view, similar to FIG. 3, illustrating another embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 serve to explain the principle of the device embodying the invention. Referring to FIG. 1, braking pulleys l, 2 and 3, mounted outside the selvage in succession in the direction of movement, represented by arrow S, of shuttle 4 entering the shuttle box, are driven at circumferential or peripheral speeds consecutively decreasing in the directions away from the selvage, the direction of rotation being indicated by the respective circular arrows, x, y, z. Considered in the same direction away from the selvage, the respective diameters of pulleys l, 2 and 3 increase, in each case, by the value 2a and, in the example of FIG. 1, the pulleys are mounted on a bar 5 so as to be rotatable about their centers M. Bar 5 extends parallel to the shuttle movement direction S. In both FIGS. 1 and 2, bar 5 is indicated only by a line and movable in a plane perpendicular to the axis of the pulleys. Also, the bar is spring loaded or biased in the direction of the shuttle guide box.

The arrangement shown in FIG. 2 differs from that shown in FIG. I in that pulleys I], I2 and I3 have equal diameters and bar 5 is mounted obliquely to the shuttle guide box, so that the centers M of each of the consecutive pulleys lie nearer the shuttle box, by the amount b, with respect to the center of the immediately preceding pulley. Otherwise, the arrangement is the same as in FIG. 1.

The systems illustrated in FIGS. 1 and 2 operate in the following manner. In both figures, the position of the parts at the moment when shuttle 4, supported by its guide support 6, has just penetrated into the gap or space between guide support 6 and a pulley 1 or 11 which is disposed closest to the selvage, is represented in solid lines. This gap may be exactly equal to the height h or thickness of the shuttle, or slightly smaller, so that, in the latter case, shuttle 4 will already, at this moment, lift pulleys 2 and 3 into the position indicated in solid lines. The cooperation between pulley 1 or pul ley 11, and shuttle 4, causes braking or deceleration of shuttle 4 to the circumferential speed of the respective pulley 1 or 11.

As is evident from FIGS. 1 and 2, at this instant, the subsequent pulley 2 or 12, which is turning at a slower circumferential speed than the associated pulley 1 or 11, is still protruding into the trajectory of shuttle 4. Thus, as soon as shuttle 4, continuing its motion in the direction away from the selvage, comes into contact with pulley 2 or 12, this pulley is pushed away from shuttle guide box 6 by amount a or b corresponding to the increasing diameters of the pulleys or, respectively, the lesser distances from centers of the pulleys to the shuttle box. Thereby, the center M of pulley 2 is dis placed upwardly by the distance a or the center M of pulley 12 by the distance b, so that bar 5 and, consequently, the two other pulleys 1 and 3, or, respectively, 11 and 13, are lifted away from the shuttle guide box 6 also by the respective distances a or b and occupy the positions indicated by the dash lines, Thereby, the first pulley l or 11 loses contact with shuttle 4.

The same motions take place again as soon as shuttle 4 engages pulley 3 or 13, each of which is turning at a still slower peripheral speed. The pulley 3 or 13, and the whole system with the two other pulleys and the bar 5, is then lifted into the position indicated by the dot and dash lines so that the preceding pulley 2 or 12 also is lifted from the shuttle 4.

In the constructional arrangement shown schematically in FIG. 3, and in a practical embodiment in FIGS. 4 and 5, two identical mechanisms 19 and 20 are provided respectively above and below the shuttle race. Therefore, only one mechanism 20 will be described. Mechanism 20 comprises braking pulleys 21, 22 and 23, rotatably mounted. in succession, in the direction away from the selvage, which has not been shown, or in the direction of shuttle movement during braking. The respective diameters of these pulleys increase in the same direction by a certain value in each case. The mechanism also includes an accelerating pulley 24 which is mounted in advance of the braking pulleys as considered in the same direction.

Braking pulleys 21, 22 and 23 are adapted to rotate about their centers M and are mounted on respective swivel arms 25, 26 and 27 which occupy an oblique position with respect to the direction S of shuttle movement and are pivotally mounted on fixed fulcrums A. Pulleys 21, 22 and 23 are driven, in the sense indicated by the respective arrows, at respective circumferential or peripheral speeds which decrease from pulley to pulley in the direction away from the selvage. All the pulley centers M and all the fulcrums A, of the swivel arms lie on parallels to the shuttle guide box or shuttle movement direction S. At pivot points B, a rod 28 is connected to the respective cranked bottom end portions 29, 30 and 31 of swivel arms 25, 26 and 27, and also extends parallel to the shuttle movement direction S. Under the bias of a spring 32 engaging a stop face 33, provided for stopping shuttle l8, rod 28 is urged to the right, as viewed in FIG. 3, and therefore toward the shuttle guide box, owing to the fact that the connection lines between the hinge points B of rod 28 and the ful crums A of the swivel arms are inclined with respect to shuttle movement direction 8.

In addition to cranking 29, the first braking pulley 21 has a cranking 34, carrying a roller 35, pivoted thereto. Roller 35 cooperates with a cam 36 whose cam surface is divided into two partial surfaces 37 and 38, of respective different diameters, which merge in the transition zone 39. In the case where partial surface 38 of cam 36 cooperates with roller 35, the guide rod system constituted by rod 28 and swivel arms 25, 26 and 27 is pivoted into a position in which pulleys 21, 22 and 23 are no longer able to cooperate with shuttle 18. On the contrary, if partial cam surface 37 engages roller 35, the respective gaps formed between the associated pulleys 21, 22 and 23 of the two pulley systems 19 and 20 are so small that shuttle 18 is able to cooperate with the braking pulleys.

Cam 36 is mounted on a cam shaft 40 carrying still another cam 41, whose cam surface comprises two par tial cam surfaces 42 and 43 of respective different di ameters and which adjoint each other at 44. The cam surface of cam 41 cooperates with a roller 45 provided on a cranked arm 46 of a swivel arm 47 which is arranged to pivot about a fixed fulcrum C and which is inclined with respect to the direction of shuttle movement during picking. Swivel arm 47 is biased toward the shuttle guide box by a spring 48. At the axis D, an acceleration pulley 24 is rotatably mounted on swivel arm 47 for rotation in the direction indicated by the associated arrow.

The cam surfaces of cams 41 and 36 have a shape and mutual arrangement such that cam 36 cooperates, through its partial surface 37 of smaller diameter, with rollers 35, when cam 41 cooperates, through its partial surface 43 of larger diameter, with roller 45. Conversely, partial surface 38 of cam 36 cooperates with roller 35 when partial surface 42, of smaller diameter, of cam 41 cooperates with roller 45. Thereby it is assured that the braking pulleys are moved into their inoperative position when accelerating pulley 24 is moved into its working position, and vice versa.

In principle, the device shown in FIGS. 3, 4 and 5 works in the manner explained in connection with FIG. 1. Pulleys 21, 22 and 23 are brought into their operative position by the action of cam 36 and, at the same time, acceleration pulley 24 is brought into its inoperative position by cam 42. The gap or distance between the two pulleys 21, of the upper system 20 and the lower system 19 is, in this case, at the most equal to the shuttle thickness )1.

As soon as shuttle 18, arriving in the picked direction S from the right, as shown in FIG. 3, i.e., from the nonrepresented selvage, penetrates between the two pulleys 21, it is braked or decelerated to the circumferential speed of these pulleys as imparted to them by the gearing 50 illustrated in FIGS. 4 and 5.

Thereupon, shuttle 18 continues in its race and passes into the gap between the two pulleys 22 which turn at a slower peripheral speed and have a slightly larger diameter relative to pulleys 21. Owing to its kinetic energy, or by being driven by either pulleys 21 or 22, shuttle l8 pushes pulleys 22, and consequently the two systems 19 and 20, so far apart as to be able to pass therebetween. Because pulleys 21, 22 and 23 are coupled by means of rod 28, pulleys 21 are lifted from the shuttle also, and all of the pulleys 21, 22 and 23 are swivelled away from the shuttle guide box along circu lar arcs about the fulcrum A. The same action occurs again as soon as shuttle 18 reaches the gap between pulleys 23, whose diameters are slightly larger than the diameters of pulleys 22. Pulleys 23 also are pushed apart by shuttle 18, so that pulleys 22 are lifted from the shuttle. Finally, shuttle 18, which at that time is already decelerated to the circumferential speed of pulleys 23, is stopped on the stop face 23.

Now, if shuttle 18 is to be picked back, counter to the direction S, braking pulleys 21, 22 and 23 are brought into their inoperative position by the earns 36, and acceleration pulleys 24 are brought into their working position by means of the cams 41. In their working position, acceleration pulleys 24 impart, to shuttle 18, a picking speed to the right, as viewed in FIG. 3, corresponding to the peripheral speeds of pulleys 24.

The differences in diameter of braking pulleys 21, 22 and 23 are so small that, in FIG. 3, they are not recognizable. For example, braking pulleys 21 have a diameter of 80 mm, pulleys 22, 81 mm and pulleys 23, 83

Instead of acceleration pulleys 24, it is also possible to provide an acceleration device. For example, a second pulley arrangement, corresponding to the two systems 19 and 20, may serve to accelerate the shuttle. The decreasing distances between the pulley peripheries and the shuttle guide, in the direction away from the selvage, also can be obtained by differentiating the angle of inclination of the swivel arms with respect to the shuttle guide.

In the embodiments of the invention described with respect to FIGS. 1 through 5, shuttle 18 is maintained pressed by the last acting pulleys 23 against the fixed stop 33. Consequently, the driven pulleys 23 slide over shuttle 18. The relative movement between the peripheries of pulleys 23 and shuttle 18 always occur at the same point of shuttle 18, and this results in a local temperature rise and in wear, which is disadvantageous.

In order to obviate this disadvantage, in accordance with a further feature of the invention, the pulleys of the last effective pair engaging the shuttle are connected frictionally with their drives. The friction drive moment of rotation of each of these pulleys is smaller than the moment of rotation resulting from the frictional force acting on the pulleys between the pulley peripheries and the shuttle.

An arrangement of this type is shown in FIG. 6, wherein the pulleys 23 are connected to their respective driving shafts 52 by means of anti-friction bearings 51. The moment of friction due to anti-friction bearings 51 is less than the moment of friction due to engagement of the peripheries of rollers 23, which are driven, with shuttle 18.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a braking and driving device, for the shuttle of a weaving loom, of the type including a plurality of driven pulleys arranged consecutively in the shuttle movement direction with at least those pulleys serving to brake the shuttle being selectively movable into a working position, in which they cooperate with a shuttle moving in a shuttle guide box, and into an inoperative position and being driven at respective peripheral speeds which decrease in the direction of shuttle movement when braked, the improvement comprising, in combination, means mounting at least those pulleys serving to brake the shuttle for conjoint displacement in a plane transverse to the pulley axes; and means biasing at least those pulleys serving to brake the shuttle toward the shuttle guide box; the respective distances between the peripheries of the braking pulleys and the shuttle path decreasing in the direction of shuttle movement when braked, with the greatest of such distances, when the peripheries of the braking pulleys are not engaged with a shuttle, being not in excess of the thickness of the shuttle, whereby said braking pulleys are successively disengaged from the shuttle solely by engagement of the shuttle with the next succeeding braking pulley.

2. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, in which the axes of the pulleys serving to brake the shuttle lie in a plane parallel to the shuttle path; the re spective diameters of the pulleys serving to brake the shuttle increasing in the direction of shuttle movement when braked.

3. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, in which the axes of the pulleys serving to brake the shuttle lie in a plane inclined toward the shuttle guide box in the direction of shuttle movement during braking; the pulleys serving to brake the shuttle having equal diameters.

4. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, including respective swivel arms mounting at least those pulleys serving to brake the shuttles; and swivel arms being pivoted to swing about respective fixed fulcrums and extending parallel to each other; a bar pivot ally connected to the swivel arms and serving to simultaneously swivel all of the swivel arms; and spring means constantly biasing said bar toward the shuttle guide box.

5. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 4, including means operatively associated with those pulleys serving to brake the shuttle to change the inclination of said swivel arms relative to the shuttle race to obtain said decrease of the respective distances between the peripheries of the pulleys serving to brake the shuttle in the direction of shuttle movement when braked.

6. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, including a driven pulley operable to accelerate the shuttle and driven in a rotational direction opposite to the rotational direction of the pulleys serving to brake the shuttle; means rotatably mounting said accelerating pulley in advance of the pulleys serving to brake the shuttle considered in the direction of shuttle movement during braking of the shuttle; and spring means biasing said acceleration pulley toward the shuttle guide box.

7. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 5, including a driven acceleration pulley rotated in a direction opposite to the direction of rotation of the pulley serving to brake the shuttle; a further swivel arm, pivoted at a fixed fulcrum, rotatably mounting said acceleration pulley in advance of said pulleys serving to brake the shuttle, considered in the direction of shuttle movement during braking; spring means biasing said further swivel arm toward the shuttle race; first and second cams mounted on a common shaft for conjoint rotation; a first follower on the swivel arm rotatably mounting the leading pulley serving to brake the shuttle and engaging said first cam; and a second follower mounted on said further swivel arm and engaging said second cam; said cams having cam surfaces effecting movement of those pulleys serving to brake the shuttle into the inoperative position in advance of movement of said acceleration pulley to engage the shuttle, and vice versa.

8. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, in which the shuttle guide box is defined by two identical systems each including said plurality of driven pulleys arranged consecutively in the shuttle shot directiori; the corresponding pulleys of each system being arranged in pairs with the pulleys of each pair being in the same plane; the two pulleys of each pair being driven at the same speed but in respectively opposite angular directions.

9. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 8, including a stop engaged by the shuttle after braking by said braking pulleys; the shuttle, when engaged with said stop, remaining in contact with the last pair of driven braking pulleys, considered in the direction of shuttle movement during braking thereof; each pulley of said last pair of braking pulleys being connected r0- tationally with its driving means through frictional contact, with the frictional drive moment of rotation of each pulley being smaller than the moment of rotation due to the frictional force acting upon the respective pulley between its periphery and the shuttle.

10. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 9, in which the means connecting each braking pulley of said last pair thereof rotationally with its drive comprises a respective anti-friction bearing interposed between the pulley and its drive.

* l I k 

1. In a braking and driving device, for the shuttle of a weaving loom, of the type including a plurality of driven pulleys arranged consecutively in the shuttle movement direction with at least those pulleys serving to brake the shuttle being selectively movable into a working position, in which they cooperate with a shuttle moving in a shuttle guide box, and into an inoperative position and being driven at respective peripheral speeds which decrease in the direction of shuttle movement when braked, the improvement comprising, in combination, means mounting at least those pulleys serving to brake the shuttle for conjoint displacement in a plane transveRse to the pulley axes; and means biasing at least those pulleys serving to brake the shuttle toward the shuttle guide box; the respective distances between the peripheries of the braking pulleys and the shuttle path decreasing in the direction of shuttle movement when braked, with the greatest of such distances, when the peripheries of the braking pulleys are not engaged with a shuttle, being not in excess of the thickness of the shuttle, whereby said braking pulleys are successively disengaged from the shuttle solely by engagement of the shuttle with the next succeeding braking pulley.
 2. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, in which the axes of the pulleys serving to brake the shuttle lie in a plane parallel to the shuttle path; the respective diameters of the pulleys serving to brake the shuttle increasing in the direction of shuttle movement when braked.
 3. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, in which the axes of the pulleys serving to brake the shuttle lie in a plane inclined toward the shuttle guide box in the direction of shuttle movement during braking; the pulleys serving to brake the shuttle having equal diameters.
 4. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, including respective swivel arms mounting at least those pulleys serving to brake the shuttles; and swivel arms being pivoted to swing about respective fixed fulcrums and extending parallel to each other; a bar pivotally connected to the swivel arms and serving to simultaneously swivel all of the swivel arms; and spring means constantly biasing said bar toward the shuttle guide box.
 5. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 4, including means operatively associated with those pulleys serving to brake the shuttle to change the inclination of said swivel arms relative to the shuttle race to obtain said decrease of the respective distances between the peripheries of the pulleys serving to brake the shuttle in the direction of shuttle movement when braked.
 6. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, including a driven pulley operable to accelerate the shuttle and driven in a rotational direction opposite to the rotational direction of the pulleys serving to brake the shuttle; means rotatably mounting said accelerating pulley in advance of the pulleys serving to brake the shuttle considered in the direction of shuttle movement during braking of the shuttle; and spring means biasing said acceleration pulley toward the shuttle guide box.
 7. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 5, including a driven acceleration pulley rotated in a direction opposite to the direction of rotation of the pulley serving to brake the shuttle; a further swivel arm, pivoted at a fixed fulcrum, rotatably mounting said acceleration pulley in advance of said pulleys serving to brake the shuttle, considered in the direction of shuttle movement during braking; spring means biasing said further swivel arm toward the shuttle race; first and second cams mounted on a common shaft for conjoint rotation; a first follower on the swivel arm rotatably mounting the leading pulley serving to brake the shuttle and engaging said first cam; and a second follower mounted on said further swivel arm and engaging said second cam; said cams having cam surfaces effecting movement of those pulleys serving to brake the shuttle into the inoperative position in advance of movement of said acceleration pulley to engage the shuttle, and vice versa.
 8. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 1, in which the shuttle guide box is defined by two identical systems each including said plurality of driven pulleys arranged coNsecutively in the shuttle shot direction; the corresponding pulleys of each system being arranged in pairs with the pulleys of each pair being in the same plane; the two pulleys of each pair being driven at the same speed but in respectively opposite angular directions.
 9. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 8, including a stop engaged by the shuttle after braking by said braking pulleys; the shuttle, when engaged with said stop, remaining in contact with the last pair of driven braking pulleys, considered in the direction of shuttle movement during braking thereof; each pulley of said last pair of braking pulleys being connected rotationally with its driving means through frictional contact, with the frictional drive moment of rotation of each pulley being smaller than the moment of rotation due to the frictional force acting upon the respective pulley between its periphery and the shuttle.
 10. In a braking and driving device for the shuttle of a weaving loom, the improvement claimed in claim 9, in which the means connecting each braking pulley of said last pair thereof rotationally with its drive comprises a respective anti-friction bearing interposed between the pulley and its drive. 